Evolution of the tetrapod limb was one of the most important advances in vertebrate history. Describe the supposed sequence in its evolution.

The limbs of tetrapods resemble the fins of lobe-finned fishes. It was believed that lobe-finned fishes were forced to make the movement onto land during droughts, when there was no water to swim in. The fish with the strongest fins survived. Because of this, the development of limbs could have surfaced as a way to find more water in times of drought.
However, this view has been changed based on fossils of acanthostega, which had tetrapod limbs but fully aquatic features. Tetrapods must have evolved their limbs underwater, then moved to land for some unknown reason.